Nice Godot game, I enjoyed spamming foxes and filthspawn in the Full Arsenal mission, good AI, and the history bar at the top is really useful. My only criticism is that those dark gray health bars look like empty health bars, which confused me when I initially saw it.
If you don't mind explaining it, I'm very curious about how you programmed the navigation for the creatures, especially the way some creatures will avoid enemies and stand behind their teammates, while others pursue their opponents aggressively.
Finally, would it be possible to implement a feature for the player to control a single character? I feel that would be fun.
Really great work.